1. Field of Invention
This invention relates to ink jet printers. More particularly, this invention is directed to apparatus and methods that allow ink jet printer control parameters to be dynamically programmed or updated.
2. Description of Related Art
An inkjet printer records information by selectively ejecting droplets of ink from a printhead to form a desired image on an image receiving medium such as a sheet of paper. A principal factor in ink jet image print quality is the print resolution, measured in dots-per-inch (dpi) horizontally and vertically. For instance, an image with a resolution of 600xc3x97600 dpi provides a much higher quality image than a 300xc3x97300 dpi resolution image.
A number of prior art systems have been directed at efforts to increase the resolution of ink jet printers. In particular, U.S. Pat. No. 5,270,728 to Lund et al., U.S. Pat. 5,029,108 to Lung, and U.S. Pat. No. 4,437,122 to Walsh et al., each of which is incorporated herein by reference in its entirety, are directed to schemes for maximizing the resolution of an ink jet printer with a given printhead. Additionally, U.S. Pat. No. 5,563,591 to Jacobs et al., which is incorporated herein by reference in its entirety, discloses an ink jet printer system in which LCD-displayed fiducial markings are repositioned to change the ink jet print resolution. The spacing of the fiducial markings on the LCD can be varied to alter the timing, positioning and movement of the carriage which holds the printhead, to the extent allowed for a given printhead of the ink jet printer.
The prior art ink jet printers attempt to enhance printer resolution by altering the print position of particular pixels or changing the pixel printing pattern subject to a given set of control parameters for a particular printhead. The resolution enhancement systems disclosed in Lund, Lung and Walsh are directed towards ink jet printers with fixed timing and control parameters set for a particular printhead configuration. In these systems, the ink jet printer image resolution is ultimately limited by the capabilities of the printhead itself. These pixel-shifting schemes, which use a given printhead, allow only a limited amount of image improvement. Jacobs"" system alters the spacing of the LCD-displayed fiducial markings, but does not change the control parameters when a new printhead is inserted.
This invention provides apparatus and methods that enable field programmable print control of ink jet printers.
Such field programmable print control alters the timing and control parameters of the ink jet printer and allows a user to replace a current printhead with a higher resolution printhead. The ink jet printer according to this invention includes a timer processing unit programmed with timing and control parameters needed by the ink jet processing unit to formulate printhead control signals. The timer processing unit is connected to a timer interface, which may be a programmable logic interface. The timer interface receives high level timing and control inputs from a data source outside the ink jet printer controller and translates them into timing and control data for programming the timer processing unit. The data source may be a personal computer, or may be stored in the printhead itself and downloaded upon replacement, or may be entered by a user or service technician via a user interface of the ink jet printer.